Pulse Jets

Bruce Simpson wrote in message . ..
...
If anyone has any specific questions then fire away and I'll do my
best to answer them.

Are you familiar with the work of Macrosonix? Would such nonlinear
resonance techniques be applicable to improving pulsejet compression
ratios?

On 7 Dec 2003 12:53:07 -0800,
(Oren Tirosh) wrote:

Bruce Simpson wrote in message . ..
..
If anyone has any specific questions then fire away and I'll do my
best to answer them.

Are you familiar with the work of Macrosonix? Would such nonlinear
resonance techniques be applicable to improving pulsejet compression
ratios?

Yes, I've seen what they're doing and although it might appear to be
applicable, there are some significant differences in the way a
pulsejet an done of their resonant systems work.

Acoustic resonators such the Macrosonix devices rely on the
accumulation of energy by the reinforcement of standing waves. This
means the energy of many separate pressure waves are accumulated into
a very large pressure differential.

By comparsion, pulsejets are a single-cycle device. The energy from
one operating cycle can't be carried over to the next and accumulated
in the same way.


----
I can be contacted via http://aardvark.co.nz/contact/

On 7 Dec 2003 12:53:07 -0800,
(Oren Tirosh) wrote:

Bruce Simpson wrote in message . ..
..
If anyone has any specific questions then fire away and I'll do my
best to answer them.

Are you familiar with the work of Macrosonix? Would such nonlinear
resonance techniques be applicable to improving pulsejet compression
ratios?

Yes, I've seen what they're doing and although it might appear to be
applicable, there are some significant differences in the way a
pulsejet an done of their resonant systems work.

Acoustic resonators such the Macrosonix devices rely on the
accumulation of energy by the reinforcement of standing waves. This
means the energy of many separate pressure waves are accumulated into
a very large pressure differential.

By comparsion, pulsejets are a single-cycle device. The energy from
one operating cycle can't be carried over to the next and accumulated
in the same way.


----
I can be contacted via http://aardvark.co.nz/contact/

On 07 Dec 2003 03:54:46 GMT,
(Allen Meece) wrote:

Are the pulse jet principles adaptable to pulse detonation rocket engines?
Can PDE's break the price/performance barrier of constant pressure rockets? I
sincerely hope so because we're up a blind alley as far as ever achieveing CATS
with the engines we've got.

Right now PDE's aren't breaking any price-performance barriers because
they're still pretty much a laboratory experiment.

Even the PDE demonstrated at Oshkosh earlier this year was totally
impractical -- requiring the use of a high-pressure centrifugal fan
driven by a fairly large conventional piston engine and a mass of
ancilliary gear -- all for a humble 200-400lbs of thrust.

I have to admit that, because my resources and time are limited, I
have not fully explored the deeper potential of PDEs so I can't give a
truly informed answer as to the realisable potential of these devices
when compared to existing CP rocket engines.


----
I can be contacted via http://aardvark.co.nz/contact/

On 07 Dec 2003 03:54:46 GMT,
(Allen Meece) wrote:

Are the pulse jet principles adaptable to pulse detonation rocket engines?
Can PDE's break the price/performance barrier of constant pressure rockets? I
sincerely hope so because we're up a blind alley as far as ever achieveing CATS
with the engines we've got.

Right now PDE's aren't breaking any price-performance barriers because
they're still pretty much a laboratory experiment.

Even the PDE demonstrated at Oshkosh earlier this year was totally
impractical -- requiring the use of a high-pressure centrifugal fan
driven by a fairly large conventional piston engine and a mass of
ancilliary gear -- all for a humble 200-400lbs of thrust.

I have to admit that, because my resources and time are limited, I
have not fully explored the deeper potential of PDEs so I can't give a
truly informed answer as to the realisable potential of these devices
when compared to existing CP rocket engines.


----
I can be contacted via http://aardvark.co.nz/contact/

What's the difference between a pulsejet and a PDE?

Thanks,


Matt Bille
)
OPINIONS IN ALL POSTS ARE SOLELY THOSE OF THE AUTHOR

What's the difference between a pulsejet and a PDE?

Thanks,


Matt Bille
)
OPINIONS IN ALL POSTS ARE SOLELY THOSE OF THE AUTHOR

MattWriter wrote:
What's the difference between a pulsejet and a PDE?

Pulsejets are just insanely loud, PDEs take insanity to a whole new level.

A pulsejet is basically a tube in which you mix fuel and air, either
pumping the air in using resonances in the piping, or using a valve that
opens when combustion is not happening.

The combustion is rapid, but not very fast.
A PDE is similar, but may not use air but oxidiser and the combustion
is designed to happen at supersonic speeds.

This can improve performance in some cases, and almost always increases
combustion chamber stress and noise.

MattWriter wrote:
What's the difference between a pulsejet and a PDE?

Pulsejets are just insanely loud, PDEs take insanity to a whole new level.

A pulsejet is basically a tube in which you mix fuel and air, either
pumping the air in using resonances in the piping, or using a valve that
opens when combustion is not happening.

The combustion is rapid, but not very fast.
A PDE is similar, but may not use air but oxidiser and the combustion
is designed to happen at supersonic speeds.

This can improve performance in some cases, and almost always increases
combustion chamber stress and noise.

On 08 Dec 2003 05:00:54 GMT, (MattWriter) wrote:

What's the difference between a pulsejet and a PDE?

A pulsejet burns its fuel by way of a mechanism called deflagration.

Deflagration is also the way fuel burns inside your car's engine.
It's a relatively gentle process and happens at quite a leisurely
pace.

The PDE burns its fuel by way of detonation (hence the name).

Detonation is a far more violent process and happens extremely
quickly.

I like to use the following as a demostration of the difference.

A gallon of gasoline has more energy than a stick of dynamite but a
gasoline burns (in normal circumstances) by way of deflagration and
dynamite detonates.

If you take your gallon of gasolone and lay a trail on the ground,
then light one end -- you'll notice that the flame travels along that
trail at a few yards a second. That's the speed of a flame front
during the deflagration process -- it's really very, very slow
compared to a detonation.

If you laid a trail of high-explosive (something that detonates) along
the same distance and set off one end -- the exposive (detonation)
proces would race along that trail at many thousands of feet per
second -- significantly faster than with the gasoline.

Another comparison would be to take the gallon of gasoline and pour it
out on the ground in a big round patch. Then stand well back and
ignite that gasoline. The result will be a very impressive "woof!" --
but it's unlikely to hurt you or even knock you over.

Now take your stick of dynamite and place it the same distance away
before setting it off. It is at this point you will notice the rather
significant difference between deflagration and detonation -- if
you're still alive that is :-)

----
I can be contacted via http://aardvark.co.nz/contact/